Generate random sequence of AlphaNumeric

December 30, 2021

I want a code to generate sequence of Alphanumeric character like LLNNLLNNLL where L is the Letter and N is the number. For example if the length is 5 the sequence will be LLNNL and if the length is 6 the sequence will be LLNNLL and if 7 it would be LLNNLLN.

string alphabets = "ABCDEFGHIJKLMNPQRSTUVWX";
int length = model.VALUE_INT;
string result = "";
for (int i = 0; i < length; i++)
{
    int next = _random.Next(23);
    result += alphabets.ElementAt(next);
    result += _randomNum.Next(1, 9);
}

This is what I have tried but condition is not fulfilling

>Solution :

For each position (value of i) of your output string you need to check if you need a character or an integer.
Since the pattern repeats every 4 positions, you can achieve this using the modulo operator:

for (int i = 0; i < length; i++)
{
    switch (i % 4)
    {
        case 0:
        case 1:
            int next = _random.Next(23);
            result += alphabets.ElementAt(next);
            break;

        case 2:
        case 3:
            result += _randomNum.Next(1, 9);
            break;
    }
}

Or another possibility: Add blocks of LLNN and then truncate the result to the needed length…

for (int i = 0; i <= (length/4); i++)
{
    result += alphabets.ElementAt(_random.Next(23));
    result += alphabets.ElementAt(_random.Next(23));
    result += _randomNum.Next(1, 9); 
    result += _randomNum.Next(1, 9); 
}
result = result.Substring(0,length);

If you want to improve these lines, you can use a StringBuilder